Polymeric foams or cellular compositions, such as polyurethane foams, are well known in the art. Polymeric foam compositions can be open celled, closed celled or mixtures thereof. Cellular polyurethane can be formed by two different processes, i.e., chemical blowing and mechanical frothing. Foamed cellular polyurethane is formed by including a foaming or blowing agent in the polyurethane composition. The blowing agent reacts with the polyurethane-forming components, or degrades upon heating, to generate a gas, such as carbon dioxide, that produces the bubbles that form the cells within the foam. By controlling other factors of the reaction and/or curing, the bubbles can remain unbroken, thereby forming a closed-cell foam, or they can be broken, thereby forming an open-cell foam. Curing of the foam can result from merely allowing sufficient time for the reaction to occur, applying heat to accelerate the reaction or applying heat to remove water and cause polymerization. All of these processes are well known in the art.
Mechanically frothed cellular polyurethane is formed by including a surfactant, such as silicon glycol copolymer, in the polyurethane composition and then mechanically stirring or shearing the composition to mix air therewith thereby forming bubbles in the liquid composition. Further stirring or shearing reduces the size of the bubbles within the foam so that course or fine grade foams can be produced. All of these processes are also well known in the art.
Cellular polyurethane is used for numerous items, such as cushions and textile coatings, and is also used to make shoe insoles, automotive trim, carpet padding, and the like.
Although polymeric foams, including polyurethane foams, have cushioning properties, it is sometimes desirable to augment the cushioning properties of the foam by combining the polymeric foam with another cushioning member. U.S. Pat. No. 4,356,642 (incorporated herein by reference) discloses a support device, such as for an innersole for footwear, that includes at least one cushion layer comprising closely spaced, discrete air pockets entrapped between plastic film. The air cushion layer is adhered to a layer of soft, flexible, open cell foam, by a layer of pressure sensitive adhesive. The patent discloses that the adhesive impregnates the foam layer and when in use under pressure, coats the plastic film, thereby reinforcing it against leakage or rupture and conforming it semi-permanently in the pressure-distorted shape.
U.S. Pat. No. 4,716,069 (incorporated herein by reference) discloses a plastic laminate material comprising a low density foamed polymeric material and a lamina of high density non-foamed polymeric material. The laminate is made in such a way that air is entrapped between the lamina. The laminate is disclosed as being useful as a protective packaging material.
Other patents disclosing multiple layers of cushioning material include U.S. Pat. Nos. 3,213,071; 3,857,731; 4,129,672 and 4,267,927.
The foregoing prior art requires the use of multiple layers, including adhesive layers, and relatively complicated methods of manufacture. Therefore, a need exists for a cushioned polymeric foam composition that is relatively simple and inexpensive to manufacture.